Expose a cached agent model and configuration discovery API

Problem

AgentOS callers can discover an ACP agent's models and configuration options only by creating a complete disposable session. That makes catalog discovery pay the full adapter spawn, ACP initialize, and session/new cost, and it couples a metadata request to session resources and credentials.

The current probe lifecycle also closes the disposable session without an awaited teardown boundary. A failed or slow probe can leave an adapter process, pending I/O, or VM resources behind and race a real foreground session for the same harness.

GigaCode has had to implement background catalog refresh, probe serialization, cached/default catalogs, per-harness configuration preparation, startup progress, and probe isolation around this lower-level behavior. Provider-response shaping belongs in GigaCode, but the expensive discovery lifecycle does not.

Proposed API

Expose a standard high-level operation that returns the agent's metadata and configuration catalog without requiring every caller to manage a disposable session, conceptually:

discoverAgentCatalog({
  agent,
  environment,
  configuration,
  software,
}) -> {
  agentInfo,
  models,
  configOptions,
  capabilities,
  fingerprint,
  source: "fresh" | "cache",
}

The exact name and shape should follow AgentOS conventions.

Required semantics

• Cache results by an AgentOS-owned fingerprint of the agent package plus configuration inputs that affect the advertised catalog.
• Deduplicate concurrent discovery for the same fingerprint.
• Keep discovery isolated from foreground sessions and their live adapter processes.
• If an adapter session is required internally, await its complete teardown before resolving.
• On failure, leave no adapter process, session record, prompt/event pump, or VM resource behind.
• Return structured stage errors such as adapter spawn failure, ACP initialize timeout, session/new timeout, adapter exit, and invalid package/configuration.
• Allow explicit invalidation/refresh while making cached reads cheap.
• Preserve the full stable ACP configOptions shape, including model and thought/reasoning selectors.
• Provide equivalent Rust, TypeScript, and actor-backed behavior.

Acceptance tests

• Two concurrent calls for one fingerprint launch at most one probe.
• A cached call creates no adapter process and performs no ACP bootstrap.
• A package/configuration fingerprint change causes one fresh discovery.
• Successful and failed fresh discovery both leave process/session counts at baseline after return.
• An initialize or session/new timeout reports its real structured stage and performs awaited cleanup.
• Manual invalidation forces a fresh result without affecting a foreground session.

Outcome

Products can render a model/configuration catalog without owning ACP probe sessions, retry actors, or cleanup workarounds, while retaining their own provider-specific response shaping and refresh UX.

No files or test paths are named. Start by tracing the existing disposable probe and session lifecycle across the Rust, TypeScript, and actor-backed implementations. Use the listed acceptance tests as the definition of done, including deduplication, caching, structured failures, and cleanup isolation.